Since a brushless direct current (BLDC) motor apparatus has no mechanical contact, it has little noise, long lifespan, simple maintenance such as no need of brush replacement or the like, etc. as compared with a motor apparatus having a brush. Accordingly, the BLDC motor apparatus has been widely used as a motor for industrial equipment, home appliances, transport systems, etc.
With regard to such motor apparatus, technology that enables the motor apparatus to rotate at higher speed, have strong start torque, and output constant power has been disclosed in Korean Patent Registration No. 10-0415493.
According to this technology, a low efficiency region, i.e., a region where a counter electromotive force is generated is not used, so that the motor apparatus can have advantages of high efficiency, high stability, simple configuration without a protective circuit, long lifespan, and convenient maintenance.
Such a conventional technology is configured to simultaneously turn on and off switching devices of an upper side (+) and a lower side (−) that constitute an H-bridge. With this configuration, in particular, when the switching device is turned off, an electric current flowing in a winding suddenly has no where to go and returns back to the (+) side via a diode connected to the switching device of the opposite upper side. At this time, there is no problem if the amount of electric current is small. However, if the amount of electric current is large, the switching device operates abnormally, so that the switching device can be reduced in lifespan or damaged.
Meanwhile, the conventional technology uses a photo-sensor or the like to sense a phase of a rotor. However, the photo-sensor additionally needs an encoder corresponding to polarity of the rotor so that the photo-sensor can sense the poles. This is the reason why the production costs of the motor apparatus increase, the structure thereof becomes complicated, and the accuracy of the motor apparatus is lowered. In addition, the photo-sensor itself is more expensive, shorter in lifespan, lower in accuracy, and lower in reliability under damp, dust or the like contaminated environment moisture than other sensors.
Further, the conventional technology includes a plurality of slots for the winding of the rotor. However, if the windings of two adjacent slots allow the electric currents to flow in the same direction, collision of magnetic fluxes causes the magnetic fluxes to offset each other and thus the efficiency of the motor apparatus decreases.